By way of example, patent document WO 00/58642 discloses an aircraft landing-gear assembly comprising:                an axle shaft arranged to carry wheels for enabling the aircraft to run on the ground;        a leg presenting a first portion carrying said axle shaft and a second portion adapted to be connected to a carrier structure of the aircraft, said leg extending along a main axis of the leg passing via said first and second leg portions;        a steering mechanism adapted to steering the first portion of the leg relative to the second portion of the leg by turning the first leg portion about a steering axis extending along the leg;        a main damper arranged to damp axial movements of the first leg portion relative to the second leg portion; and        a first secondary damper adapted to damping angular oscillating motion of the first leg portion relative to the second leg portion about said steering axis.        
That type of aircraft landing-gear assembly is provided with a steering mechanism for steering the axle shaft that carries the wheels relative to the second leg portion that is connected to the carrier structure of the aircraft.
With that type of landing-gear assembly, while running on the ground, a vibratory phenomenon commonly known as “shimmy” may appear. That vibratory phenomenon may create discomfort, and in worst-case scenarios it can lead to certain parts of the landing-gear assembly breaking. It is thus desirable to eliminate such scenarios.
These vibratory/oscillatory phenomena depend on several factors such as the load on the landing-gear assembly, its shape, its design, its flexibility, its running speed.
In order to attenuate that phenomenon, patent document WO 00/58642 suggests fitting a particular damper, which it refers to as a “shimmy” damper, and which is referred to below as a “secondary” damper. In that patent document, the secondary damper couples together the second portion of the leg that is connected to the structure of the aircraft and the first portion of the landing-gear assembly leg that carries the axle shaft. That mechanical coupling of the first and second portions of the leg via the secondary damper (shimmy damper) serves to damp the relative angular oscillations between the first and second portions of the leg about the main axis of the leg, which in that embodiment is parallel to and coincides with the steering axis of the first leg portion.
Incorporating that type of shimmy damper into the structure of the landing gear is problematic since the secondary damper needs to be able to perform its damper function while also allowing the landing gear to pass between a deployed configuration outside the landing-gear bay and a retracted configuration in which it is located inside the landing-gear bay.